Powder particles, powder paint composition containing powder particles and fluororesin, and manufacturing methods thereof

Abstract

An object of the present invention is to provide powder particles for improving the adhesive strength between a substrate and a fluororesin layer. The present invention is powder particles obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion.

Description

TITLE OF THE INVENTIONPOWDER PARTICLES, POWDER PAINT COMPOSITION CONTAINING POWDER PARTICLES AND FLUORORESIN, AND MANUFACTURING METHODS THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Japanese Patent Application No. 2023-141274 filed August 31 , 2023, the disclosures of which are incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to: powder particles that improve adhesion between a substrate and a fluororesin layer; and a powder paint composition containing powder particles and fluororesin, which is useful as a primer. Furthermore, the present invention also relates to manufacturing methods of these powder particles and powder paint composition.CONVENTIONAL TECHNOLOGY

[0003] Fluororesins have excellent chemical resistance, non-pressuresensitive adhesion, heat resistance, electrical insulation properties, and the like, and have been widely conventionally used as coating materials. Fluororesins have non-pressure-sensitive adhesion, which tends to cause adhesive defects when coated directly to substrates (in particular, various metal substrates). Therefore, in many cases, a primer layer having favorable adhesion to a substrate is provided as an undercoat layer for fluororesins.

[0004] The present applicant proposed polymer particles with excellent adhesion between a substrate and layer and that prevent peeling due to heat, moisture, or the like, and a paint composition containing the polymer particles (Patent Document 1 ). The paint composition has an excellent effect, but has some problems, such as the use of organic solvents in the preparation of polymer particles, which may cause an environmental burden, the resulting paint composition being an aqueous dispersion, which requires the addition of a surfactant to ensure the dispersibility of the fluororesin, and the like.

[0005] On the other hand, powder coatings are known to have the advantages of being environmentally friendly because a solvent is not used, being resource-efficient because powders can be easily reused, having excellent coating workability, and the like. Patent Document 2 discloses a powder primer composition containing a meltable fluororesin powder and polyethersulfone powder. However, there is still a need for paint compositions with superior adhesion and corrosion resistance.PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0006] [Patent Document 1] Japanese Unexamined Patent Application 2013- 231098

[0007] [Patent Document 2] Japanese Unexamined Patent Application 2022-137848

[0008] [Patent Document 3] Japanese Unexamined Patent Application 2007-320267SUMMARY OF THE INVENTIONPROBLEM TO BE SOLVED BY THE INVENTION

[0009] An object of the present invention is to provide powder particles having excellent adhesive strength between a substrate and a fluororesin layer, and to provide a powder paint composition that, by containing the powder particles, can prevent a fluororesin laminate body from peeling off and improve corrosion resistance, steam resistance, and durability by suppressing the penetration of heat, moisture, corrosive substances, and the like through excellent adhesion. Furthermore, an object of the present invention also provides manufacturing methods of these powder particles and powder paint composition.MEANS FOR SOLVING THE PROBLEM

[0010] One embodiment of the present invention is powder particles obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion. In the powder particles, the hot-melt polymer and filler are preferably fused. The hot-meltpolymer is preferably at least one selected from polyimide, polyamideimide, polyamide, polyester, polyethylene terephthalate, polyphenylene sulfide, polysulfone, polyetherimide, polyethersulfone, polyether ether ketone, and polyether ketone ketone, and more preferably at least one selected from polyphenylene sulfide, polyetherimide, polyether ether ketone, and polyether ketone ketone. Furthermore, the filler is preferably at least one of inorganic particles selected from silicon carbide, silicon oxide, aluminum oxide, zinc oxide, tin oxide, titanium oxide, barium sulfate, and carbon black. The powder particles preferably contain 30 to 300 parts by weight of the filler with respect to 100 parts by weight of the hot-melt polymer. The particle size is preferably 150 pm or less.

[0011] Furthermore, one embodiment of the present invention is a powder paint composition containing: powder particles obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion; and a fluororesin powder. The fluororesin powder preferably contains a hot-melt fluororesin, and more preferably is a perfluororesin. Furthermore, the present invention is the powder paint composition containing 80 to 50 weight% of the powder particles and 20 to 50 weight% of the fluororesin powder, based on the total amount of the powder paint composition.

[0012] Furthermore, one embodiment of the present invention is a method of manufacturing powder particles, including:(1) a step of mixing a hot-melt polymer and filler in water to obtain an aqueous dispersion;(2) a step of heating the aqueous dispersion and removing water to obtain a solid; and(3) a step of pulverizing the solid to obtain powder particles. After step (2), a step of heating at a temperature at or higher than the glass transition point of the hot-melt polymer is preferably further included.

[0013] Furthermore, one embodiment of the present invention is a method of manufacturing a powder paint composition, including:(1) a step of mixing a hot-melt polymer and filler in water to obtain an aqueous dispersion;(2) a step of heating the aqueous dispersion and removing water to obtain a solid;(3) a step of pulverizing the solid to obtain powder particles; and(4) a step of adding a fluororesin powder to the powder particles and mixing to obtain a powder paint composition.EFFECT OF THE INVENTION

[0014] The powder paint composition of the present invention has excellent adhesive strength between a substrate and fluororesin layer, and prevents the fluororesin laminate body from peeling off by suppressing the penetration of heat, moisture, corrosive substances, and the like, thereby obtaining a coating film with improved corrosion resistance, steam resistance, and durability. Therefore, it can be widely applied to OA applications, chemical corrosion prevention applications, food heating and processing equipment applications, sliding material applications, automotive applications, construction material applications, members for a semiconductor manufacturing device, and the like.

[0015] Furthermore, the powder paint composition of the present invention does not require the addition of a surfactant and does not use an organic solvent in a manufacturing process thereof, which also has the advantage of having a low environmental burden. Furthermore, the powder paint composition of the present invention can improve the purity of a coating film and obtain more favorable performance by not adding a surfactant in a coating film manufacturing process.MODE FOR CARRYING OUT THE INVENTION1 . Powder Particles

[0016] The powder particles of the present invention are powder particles in which (A) a hot-melt polymer and (B) a filler are fused. The powder particles can be obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion.A. Hot-Melt Polymer

[0017] The hot-melt polymer of the present invention is a polymer that melts upon heating and has a glass transition point and / or melting point. Specific examples of the hot-melt polymer include polyimide (PI), polyamideimide (PAI), polyamide, polyester, polyethylene terephthalate, polyphenylene sulfide, polysulfone, polyetherimide, polyethersulfone (PES), polyether ether ketone, polyether ketone ketone, and the like. Of these hot- melt polymers, polyetherimide (PEI), polyphenylsulfone (PPS), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), and the like are preferred due to having heat resistance and high mechanical strength. Hot-melt polymers are used by fusing with a filler, and therefore, the hot-melt polymer used in the present invention does not include a fluororesin, which generally has excellent non-pressure-sensitive adhesion. The shape of the hot-melt polymer is not particularly limited, but can be, for example, powder, granular or granulated granules, pellets, and the like. The average particle size of the hot-melt polymer is preferably 0.1 to 300 pm, more preferably 1 to 100 pm, and even more preferably 5 to 70 pm.

[0018] Commercially available hot-melt polymers can be used. Examples of commercially available hot-melt polymers include the ULTEM® series available from SABIC, PPS available from DIC Corporation, and the like.B. Filler

[0019] Inorganic particles can be used as the filler of the present invention, and can be selected according to the application of the coating film in consideration of the water resistance, chemical resistance, and the like thereof. The filler of the present invention is preferably prepared from a material that does not dissolve in water. Specific examples of fillers include metal powders, metal oxides (aluminum oxide, zinc oxide, tin oxide, titanium oxide, and the like), glass beads, glass flakes, glass particles, ceramics, silicon carbide, silicon oxide, calcium fluoride, carbon black, graphite, mica, barium sulfate, and the like. The filler of the present invention has a heat resistance ofat least 200°C or higher, and preferably 300°C or higher, and preferably does not promote decomposition of fluororesins. Silicon oxide, aluminum oxide, zinc oxide, tin oxide, and barium sulfate are preferred among the fillers above. The particle size of the filler is not particularly limited but is preferably smaller than the average particle size of the hot-melt polymer from the perspective of facilitating uniform mixing with the hot-melt polymer. The average particle size of the filler is preferably 0.1 to 30 pm, more preferably 0.2 to 20 pm, and even more preferably 0.3 to 10 pm.Powder Particles of Present Invention

[0020] The powder particles of the present invention are powder particles in which (A) a hot-melt polymer and (B) a filler are fused. The powder particles can be obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion. The particle size of the filler is preferably small. However, if the step includes a pulverizing step described later, the filler is also pulverized in this step. Thus, the particle size of the filler used is not particularly limited. The amount of the filler added is 30 to 300 parts by weight, preferably 50 to 200 parts by weight, and more preferably 80 to 150 parts by weight, with respect to 100 parts by weight of the polymer.

[0021] The particle size of the powder particles of the present invention is preferably 1 to 200 pm, and even more preferably 150 pm or less. For example, use of a 150 pm mesh sieve to collect particles that pass through the sieve can obtain particles with a particle size of 150 pm or less in size, typically approximately 5 to 150 pm. By using a sieve, particles of a uniform particle size can be easily obtained.

[0022] In general, fluororesins have non-pressure-sensitive adhesive properties and do not adhere well to fillers. Therefore, if the contact interface between the fluororesin and the filler increases, a filler portion and a fluororesin laminate body easily peel off, causing inferior corrosion resistance, steam resistance, and durability in this portion. In contrast, the powder particles of thepresent invention can reduce the contact interface between the filler and the fluororesin added later by fusing and integrating the hot-melt polymer and filler as described above. As a result, the adhesive strength between a substrate and fluororesin layer is excellent, and the fluororesin laminate body can be prevented from peeling off by suppressing the penetration of heat, moisture, corrosive substances, and the like, thereby obtaining a coating film with improved corrosion resistance, steam resistance, and durability.2. Powder Paint Composition

[0023] The powder paint composition of the present invention is a composition containing: the powder particles in which (A) a hot-melt polymer and (B) a filler are fused; and (C) a fluororesin powder.C. Fluororesin

[0024] Examples of the fluororesin of the present invention include, but are not limited to, polytetrafluoroethylenes (PTFE), tetrafluoroethylene perfluoro (alkyl vinyl ether) copolymers (PFA), tetrafluoroethylene hexafluoropropylene copolymers (FEP), tetrafluoroethylene hexafluoropropylene perfluoro (alkyl vinyl ether) copolymers, tetrafluoroethylene ethylene copolymers, polyvinylidene fluorides, polychlorotrifluoroethylenes, chlorotrifluoroethylene ethylene copolymers, and the like.

[0025] The fluororesin of the present invention is preferably a hot-melt fluororesin that exhibits melt flowability at or above a melting point. From the perspective of non-pressure-sensitive adhesion and heat resistance of a coating film, a hot-melt perfluororesin, such as a low molecular weight PTFE, PFA, FEP, tetrafluoroethylene hexafluoropropylene perfluoro (alkyl vinyl ether) copolymer, or the like is preferably used, with PFA being particularly preferably used.

[0026] The alkyl group of the perfluoro (alkyl vinyl ether) in the PFA preferably has 1 to 5 carbon atoms, and of these, perfluoro (propyl vinyl ether) (PPVE), perfluoro (ethyl vinyl ether) (PEVE), and perfluoro (methyl vinyl ether) (PMVE) are particularly preferable. The amount of perfluoro (alkyl vinyl ether) in the PFA is preferably in a range of 1 to 50 weight%.

[0027] The fluororesin used in the present invention has a melt flow rate (MFR) of (1 to 100) g / 10 min at 372°C ± 1 °C, and preferably (1 to 70) g / 10 min, and is preferably melt moldable. Herein, several copolymers with different MFRs can be mixed to obtain a melt flow rate (MFR) of (1 to 100) g / 10 min, and preferably (1 to 70) g / 10 min at 372°C ± 1°C.

[0028] Furthermore, fluororesin particles with a so-called core-shell structure containing fluororesins with different melting points may also be used as the fluororesin in the present invention, as described in Patent Document 3, for example. Fluororesins having a multilayer structure with at least two types of fluororesins with different melting points preferably contain 90 to 5 weight% of a fluororesin in an outermost layer and 10 to 95 weight% of a high- melting point fluororesin in an inner layer. The ratio of the outermost layer to the inner layer can be selected based on the desired chemical resistance and gas permeability, linear expansion coefficient, maximum strength, and the like. Such fluororesins can be obtained as PFA particles containing PTFE, for example, by dispersing PTFE particles in a polymerization medium in a PFA polymerization tank in advance to initiate polymerization of PFA.

[0029] The fluororesin powder of the present invention may be any of the aforementioned fluororesin powders, and the average particle size thereof is 0.05 to 75 pm, preferably 5 to 40 pm, and more preferably 5 to 30 pm. The fluororesin powder of the present invention can be obtained by powderizing the aforementioned fluororesin using a conventionally known method, or a commercially available product may be used. Examples of commercially available products include Teflon® MJ-102, MJ-103, and the like available from Chemours-Mitsui Fluoroproducts Co., Ltd., Teflon® 532G-5011 available from Chemours, and the like.Powder Paint Composition of Present Invention

[0030] The powder paint composition of the present invention is a composition containing the powder particles of the present invention and the fluororesin powder, in other words, a composition containing: the powderparticles in which (A) the hot-melt polymer and (B) the filler are fused; and (C) the fluororesin powder. The powder paint composition of the present invention contains 80 to 50 weight% of the powder particles and 20 to 50 weight% of the fluororesin powder, preferably contains 75 to 55 weight% of the powder particles and 25 to 45 weight% of the fluororesin powder, and more preferably contains 60 to 70 weight% of the powder particles and 40 to 30 weight% of the fluororesin powder, based on the total amount of the powder paint composition. If the amount of the fluororesin powder is too high, adhesion with a substrate may decrease, and if the amount is too low, adhesion with another fluororesincontaining layer may decrease.Optional Components

[0031] In addition to the powder particles and fluororesin powder, the powder paint composition of the present invention may further contain an optional additive, if necessary. The additives above are not particularly limited and include, for example, those used in general paint compositions, and the like. Examples of the additives above include pigments, fillers, leveling agents, solid lubricants, moisture absorbers, surface modifiers, UV absorbers, light stabilizers, plasticizers, anti-coloring agents, anti-scratch agents, anti-fungal agents, antibacterial agents, antioxidation agents, antistatic agents, silane coupling agents, and the like.

[0032] Specific examples of the additive include carbon, titanium oxide, red iron oxide, mica and other color pigments, anti-corrosive pigments, fired pigments, body pigments, photoluminescent polarizing pigments, scale pigments, wood powder, quartz sand, carbon black, clay, talc, diamond, fluorinated diamond, corundum, silica stone, boron nitride, boron carbide, silicon carbide, fused alumina, tourmaline, jade, germanium, zirconium oxide, zirconium carbide, chrysoberyl, topaz, beryl, garnet, glass, glass powder, mica powder, metal powder (gold, silver, copper, platinum, stainless steel, aluminum, and the like), various reinforcing materials, various reinforcing and bulking materials, conductive fillers, and the like.

[0033] The amount of the additive above is preferably 0 to 10.0 weight%, and more preferably 0 to 5.0 weight% with respect to the powder composition above. The powder paint composition of the present invention is ordinarily suitably used as a primer coating (undercoat) for adhering a fluororesin layer to a substrate. However, the composition can also be used as a one-coat coating that does not use a primer coating.Preparation of Coating Film

[0034] The powder paint composition of the present invention can be applied to a substrate and heated to form a coating film. The substrate is not particularly limited and includes iron, aluminum, copper, stainless steel, and other metal substrates, glass, ceramics, and heat-resistant plastic substrates, and the like. The method of application to the substrate above is not particularly limited and can be selected according to the form of the substrate and the like. For example, conventionally known methods such as electrostatic powder coating and the like can be employed. The thickness of the coating depends on the application. For example, coating is possible at 20 to 150 pm, and preferably 30 to 100 pm.

[0035] The coating film containing the powder paint composition of the present invention has excellent corrosion resistance, steam resistance, and adhesion to the substrate as well as non-pressure-sensitive adhesion. Therefore, it can be widely applied to OA applications, chemical corrosion prevention applications, food heating and processing equipment applications, sliding material applications, automotive applications, construction material applications, members for a semiconductor manufacturing device, and the like.3. Manufacturing Methods of Powder Particle and Powder Paint CompositionManufacturing Method of Powder Particles

[0036] The powder particles of the present invention can be obtained by the following steps (1 ) to (3).(1) a step of mixing a hot-melt polymer and filler in water to obtain an aqueous dispersion;(2) a step of heating the aqueous dispersion and removing water to obtain a solid; and(3) a step of pulverizing the solid to obtain powder particles.

[0037] In step (1 ), the hot-melt polymer and filler are added to water and dispersed. The water used herein is preferably water that is usually referred to as pure water, from which impurities such as ions and the like have been removed by a distillation method or ion exchange method. As a method for dispersing the hot-melt polymer and filler, a homogenizer, ultrasonic disperser, colloid mill, bead mill, or the like can be used in addition to the usual dispersion process using an mixer. Although a dispersant such as a surfactant or the like may be added herein, the dispersant is preferably not added from the perspective of reducing the environmental burden.

[0038] In step (2), the dispersion obtained in step (1 ) is heat-dried to remove moisture. Drying temperatures of 60 to 160°C, preferably 80 to 140°C, and more preferably 100 to 120°C can be used, for example. The drying time can be 5 minutes to 10 hours, preferably 1 hour to 8 hours, more preferably 2 hours to 6 hours, and even more preferably 3 hours to 5 hours. Regarding the devices used for drying, acceptable methods for drying include a method of drying in an oven set at a prescribed temperature, and a method of using, for example, an arch dryer, a floating dryer, a drum dryer, an infrared dryer, or the like. An organic solvent is not used in the manufacturing method of the present invention, and therefore, the drying step can be carried out without the need for special facilities such as explosion-proof equipment and the like.

[0039] After step (2), a step of heating at a temperature at or higher than the glass transition point of the hot-melt polymer is preferably included. By including this step, powder particles in which the hot-melt polymer and filler are fused can be obtained. By obtaining the powder particles in which the hot-melt polymer and filler are fused, it is more difficult for the filler to detach from the powder particles, resulting in a coating film with superior corrosion resistance and steam resistance.

[0040] Step (3) is a step of pulverizing the solid obtained in step (2). For example, a high-pressure homogenizer, grinder, impact pulverizer, bead mill, jet mill, hammer mill, pin mill, ball mill, tube mill, pulverizing mill, air sweep mill, disk mill, vibration mill, stone mill, planetary motion mill, or other pulverizer can be used as the pulverizing method. After pulverization, the particle size is preferably adjusted using a sieve. The mesh opening of the sieve used can be selected, as appropriate, according to the size of the particles obtained in step (3), but 150 pm or less is preferred from the perspective of the uniformity of the powder paint composition.Manufacturing Method of Powder Paint Composition

[0041] The powder paint composition of the present invention can be manufactured by step (4) adding and mixing a fluororesin powder in addition to steps (1) to (3) in the aforementioned method of manufacturing powder particles. For mixing, any conventionally known method of mixing powders can be used. For example, any of the following methods can be used: method of placing powders to be mixed in a single container and rotating the container itself; a method of mixing with a mixing blade in a container containing powders to be mixed; a method of stirring and mixing with an air current; or the like.EXAMPLES

[0042] The present invention will be described below in further detail based on examples and comparative examples. However, the present invention is not limited to these examples.Raw materialsA. Hot-Melt Polymer1. Polyetherimide (PEI)ULTEM 101 OP powder (available from SABIC INNOVATIVE PLASTICS, glass transition point: 217°C)2. Polyphenylene sulfide (PPS)Available from DIC Corporation, average particle size: 12 to 16 pm, melting point: 278°C3. Polyether ether ketone (PEEK)VICOTE® 704 (available from VICTREX, melting point: 343°C)4. Polyether ketone ketone (PEKK)KSTONE® CC-5601 (available from Shandong Kaisheng New Materials, melting point: 308°C)B. Filler1. Barium sulfate (BaSC )BLANC FIXE MICRO (available from SACHTLEBEN, average particle size: 0.8 pm)2. Aluminum oxide (AI2O3)SGA-16 (available from ALMATIS, average particle size: 0.4 pm)3. Carbon black (CB)MPC Channel Black (available from Keystone Aniline)C. FluororesinPFA (MJ-102, available from Chemours-Mitsui Fluoroproducts Co., Ltd. , average particle size: 20 pm) Example 1Preparation of the Powder Paint Composition

[0043] (Step (1 )) 3.2 L of pure water was placed in a 5 L beaker, 1 kg of barium sulfate and 1 kg of PEI were added, and the mixture was stirred at 300 rpm for 30 minutes using a mixer (available from YAMATO SCIENTIFIC CO. LTD.).

[0044] (Step (2)) The dispersion obtained in step (1 ) was placed in an oven set at 120°C for 2 hours to remove moisture. It was further placed in an oven set at 300°C for 2 hours.

[0045] (Step (3)) The solid obtained in step (2) was crushed in a mill pulverizer (available from Osaka Chemical Co., Ltd.) at 25,000 rpm. It was then passed through a 150 pm mesh sieve to obtain powder particles.

[0046] (Step (4)) 350 g of PFA was added to 650 g of the powder particles obtained in step (3) to obtain a powder paint composition. The blending ratio of PEI: BaSO4: PFA is 32.5%: 32.5%: 35.0%.Preparation of Test Piece

[0047] Aluminum (A1050) of 50 mm x 100 mm was used as a substrate, masked approximately 10 mm on one side, and shot blasted with #60 alumina. Thereafter, the aforementioned powder paint composition was applied by electrostatic powder coating using a powder coating spray gun (GX355HW available from PARKER IONICS) to form a primer layer with a film thickness of 50 pm. The masking tape was removed, PFA (MJ-102) was applied by electrostatic powder coating on the primer layer using a powder coating spray gun, and baked at 390°C (substrate temperature) for 30 minutes to form a topcoat layer, and the resulting fluororesin laminate body was used as a test piece.Measurement of Adhesive Strength

[0048] Using the test piece above, the fluororesin laminate body was cut 10 mm wide in a short side direction, and a masked portion (fluororesin laminate body portion without primer layer) was peeled off from the masked portion toward the portion of the fluororesin laminate body with the primer layer. The peeled off masked portion (fluororesin laminate body without a primer layer) was protected with masking tape. Using a Tensilon universal testing machine (available from A&D), the portion protected by the masking tape was placed between chucks of the testing machine and pulled at a rate of 50 mm / min to measure the adhesive strength of the fluororesin laminate body portion with a primer layer, in accordance with a method of measuring the peel strength of an adhesive (90-degree peel test method) as specified in JIS K 6854 using a Tensilon universal testing machine (available from A&D). The units were gf / cm. The adhesive strength was measured on each of the test pieces before and after performing the steam resistance test described later.Steam Resistance Test

[0049] Using a pressure cooker tester (PCT VS-277, available from Kyosin Engineering Corporation), the above test pieces were left in water vapor at 170°C and 0.8 MPa for 300 hours, then left to cool to ambient temperature. The presence or absence of blisters (rash-like swelling) was observed visually and under a microscope. Blisters were rated "O" if no blisters were observed and "X" if blisters were observed. The test pieces after the steam resistance test were used to perform the adhesive strength measurement described above.Examples 2 to 4

[0050] Test pieces were obtained in the same manner as in Example 1 , except that instead of PEI: 32.5% and barium sulfate: 32.5% in Example 1 , the added amounts were changed such that the blending ratios were as shown in Table 1 .Example 5

[0051] Test pieces were obtained in the same manner as in Example 1 , except that PEEK was used instead of PEI in Example 1 and step 2 was performed at the following temperatures.(Step (2) (Example 5))

[0052] The dispersion obtained in step (1 ) was placed in an oven set at 120°C for 2 hours to remove moisture. The dispersion was further placed in an oven at 350°C for 2 hours.Example 6

[0053] Test pieces were obtained in the same manner as in Example 1 , except that PEKK was used instead of PEI in Example 1 and step 2 was performed at the following temperatures.(Step (2) (Example 6))

[0054] The dispersion obtained in step (1) was placed in an oven set at 120°C for 2 hours to remove moisture. It was further placed in an oven at 310°C for 2 hours.Example 7

[0055] Test pieces were obtained in the same manner as in Example 1 , except that step (2) in Example 1 was changed to the following step (2').(Step (2’))

[0056] The dispersion obtained in step (1) was placed in an oven set at 120°C for 2 hours to remove moisture.Example 8

[0057] Test pieces were obtained in the same manner as in Example 5, except that step (2) in Example 5 was changed to the following step (2').(Step (2’))

[0058] The dispersion obtained in step (1) was placed in an oven set at 120°C for 2 hours to remove moisture.Comparative Example 1

[0059] Acomposition was obtained by mixing 325 g of PEI, 325 g of barium sulfate and 350 g of PFA by weight. The blending ratio of PEI: BaSO4: PFA is 32.5%: 32.5%: 35.0%. The obtained composition was used to obtain test pieces as in Example 1 (Preparation of Test Piece).Comparative Examples 2 to 6

[0060] Test pieces were obtained in the same manner as in Comparative Example 1 , except that instead of PEI: 32.5% and barium sulfate: 32.5% in Comparative Example 1 , the added amounts were changed such that the blending ratios were as shown in Table 1 .

[0061] The blending ratios and test results for the examples and comparative examples are shown in Table 1. Although the compositions ofExample 1 and Comparative Example 1 are the same, Example 1 uses a powder paint composition prepared by the manufacturing method of the present invention, while Comparative Example 1 simply uses a composition obtained by mixing materials. It can be seen that the adhesive strength is clearly greater in Example 1. Similar results were obtained in Comparative Examples 2 to 6, which correspond to Examples 2 to 4 and 6 to 8.Table 1

[0062] The present invention is not limited to the disclosed content of the examples described in the present specification or to the embodiments of the invention disclosed in the present specification, and encompasses the content of inventions appropriately modified based on the particularsdisclosed in the present and the like, so long as the content does not conflict with the gist of the present invention.INDUSTRIAL APPLICABILITY

[0063] The powder paint composition of the present invention has excellent adhesive strength between a substrate and fluororesin layer and prevents the fluororesin laminate body from peeling off by suppressing the penetration of heat, moisture, corrosive substances, and the like, thereby obtaining a coating film with improved corrosion resistance, steam resistance, and durability.

Claims

Claims1 . Powder particles obtained by pre-mixing a hot-melt polymer and a filler in water to obtain an aqueous dispersion and then heating the aqueous dispersion.

2. The powder particles according to claim 1 , wherein the hot-melt polymer and filler are fused.

3. The powder particles according to claim 1 , wherein the hot-melt polymer is at least one selected from polyimide, polyamideimide, polyamide, polyester, polyethylene terephthalate, polyphenylene sulfide, polysulfone, polyetherimide, polyethersulfone, polyether ether ketone, and polyether ketone ketone.

4. The powder particles according to claim 1 , wherein the hot-melt polymer is at least one selected from polyphenylene sulfide, polyetherimide, polyether ether ketone, and polyether ketone ketone.

5. The powder particles according to claim 1 , wherein the filler is at least one of inorganic particles selected from silicon carbide, silicon oxide, aluminum oxide, zinc oxide, tin oxide, titanium oxide, barium sulfate, and carbon black.

6. The powder particles according to claim 1 , comprising 30 to 300 parts by weight of the filler with respect to 100 parts by weight of the hot-melt polymer.

7. The powder particles according to claim 1 , wherein the particle size is 150 pm or less.

8. A powder paint composition, comprising: the powder particles according to any one of claims 1 to 7; and a fluororesin powder.

9. The powder paint composition according to claim 8, wherein the fluororesin powder contains a hot-melt fluororesin.

10. The powder paint composition according to claim 8, wherein the fluororesin powder contains a perfluororesin.

11. The powder paint composition according to claim 8, comprising 80 to 50 weight% of the powder particles and 20 to 50 weight% of the fluororesin powder, based on the total amount of the powder paint composition.

12. A method of manufacturing powder particles, comprising:(1) a step of mixing a hot-melt polymer and filler in water to obtain an aqueous dispersion;(2) a step of heating the aqueous dispersion and removing water to obtain a solid; and(3) a step of pulverizing the solid to obtain powder particles.

13. The method of manufacturing powder particles according to claim 12, further comprising, after step (2), a step of heating at a temperature at or higher than the glass transition point of the hot-melt polymer.

14. A method of manufacturing a powder paint composition, comprising:(1) a step of mixing a hot-melt polymer and filler in water to obtain an aqueous dispersion;(2) a step of heating the aqueous dispersion and removing water to obtain a solid;(3) a step of pulverizing the solid to obtain powder particles; and(4) a step of adding a fluororesin powder to the powder particles and mixing to obtain a powder paint composition.

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